TECHNICAL FIELD
[0001] This invention relates to a manganese-zinc system ferrite for use as cores of electric
power supplies, typically power supply transformers operating at a high frequency
of about 10 to 500 kHz and a core for power supply constructed by the ferrite.
BACKGROUND ART
[0002] Manganese-zinc system ferrite is often used to form cores for use in coils and transformers
of various communication equipment and commercial appliances. Since the recent trend
is to use power supplies of higher frequency, core materials of performance meeting
such purposes are now required. In particular, switching power supplies need transformers
which operate at a power of several tens of watts and a high frequency band of 10
to 500 kHz. Also required are cores for transformers intended for motor drive, signal
amplification and oscillation purposes. Transformer cores are conventionally formed
of low-loss ferrites of manganese-zinc system. However, since the power loss also
known as core loss is substantial in a high frequency region of 10 to 500 kHz, there
is a demand for an improvement in core loss. Various proposals have been made in this
respect.
[0003] Such proposals included addition of oxides of Si and Ca and further addition of oxides
of tetravalent metals such as Sn, Ti and Zr as well as oxides of pentavalent metals
such as V, Nb and Ta. Examples of the sole or combined addition of oxides of tetra-
or pentavalent metals are found in Japanese Patent Application Kokai (JP-A) Nos. 2880/1971,
72696/1973, 262404/1985, 108109/1986, 252609/1986, 252611/1986, 222018/1988, 129403/1989,
54902/1990, 141611/1991, 163804/1991, 223119/1991, 248403/1991, 248404/1991, 248405/1991,
254103/1991, 55362/1992, 150007/1992, 198416/1993, 267040/1993, etc.
[0004] These proposals, however, fail to increase the difference between maximum magnetic
flux density Bm and residual magnetic flux density Br, ΔB = Bm - Br, at a high frequency
of e.g., 100 kHz and 100°C, to reduce the power loss at the high frequency, and to
increase effective magnetic permeability (µa) associated with a µa-B curve. As a consequence,
when transformers are formed of these conventional ferrites, it is difficult to reduce
the size of transformers.
[0005] From Data Base WPI Week 9347 Derwent Publications Ltd., London, GB; AN 93-371315
XP002009966 & JP-A-05 267 040, 15 October 1993, a lower loss Mn-Zn ferrite for a switching
power transformer core is known which comprises MnO, ZnO and Fe
2O
3 as main components, Si
3N
4 and CaO as auxiliary components and at least one oxide of Nb, Ti, Sb, Ta, Zr, Sn,
Co or Si. Si
3N
4 is one inevitable component of the known ferrite.
DISCLOSURE OF THE INVENTION
[0006] An object of the present invention is to provide a ferrite having a low power loss
as well as large ΔB = Bm - Br at high frequency and an improved µa-B curve and a core
for a power supply using the same.
[0007] This and other objects are achieved by the present invention which is defined below
as (1) to (11).
(1) A ferrite characterized by comprising
manganese oxide, zinc oxide, and iron oxide as main components, and
silicon oxide, calcium oxide, tin oxide and/or titanium oxide, niobium oxide, and
zirconium oxide as subordinate components, wherein
in the main components, the content of manganese oxide is 30 to 41 mol% calculated
as MnO and the content of zinc oxide is 6 to 16 mol% calculated as ZnO, and
the weight proportion of the subordinate components based on the main components is
such that
silicon oxide is 50 to 250 ppm calculated as SiO2,
calcium oxide is 200 to 1,500 ppm calculated as CaO, tin oxide is up to 4,000 ppm
calculated as SnO2, titanium oxide is up to 3,000 ppm calculated as TiO2, and the total of tin oxide and titanium oxide is at least 300 ppm,
niobium oxide is from 100 to 500 ppm calculated as Nb2O5, and
zirconium oxide is from 50 to 400 ppm calculated as ZrO2, said ferrite being free from Si3N4.
(2) The ferrite of (1) wherein the weight ratio of P based on the main components
is 0 to 30 ppm.
(3) The ferrite of (1) or (2) wherein the weight ratio of B based on the main components
is 0 to 50 ppm.
(4) The ferrite of any one of (1) to (3) which has a power loss of up to 300 kW/m3 at a temperature of 100°C when an AC magnetic field of 100 kHz and 200 mT is applied.
(5) The ferrite of (4) which has an eddy current loss of up to 200 kW/m3 at a temperature of 100°C when an AC magnetic field of 100 kHz and 200 mT is applied.
(6) The ferrite of any one of (1) to (5) wherein when an AC magnetic field of 100
kHz is applied at a temperature of 100°C, the resulting hysteresis curve has a ΔB
value of at least 220 mT wherein ΔB = Bm - Br wherein Bm and Br are maximum magnetic
flux density and residual magnetic flux density, respectively.
(7) The ferrite of any one of (1) to (6) wherein when an AC magnetic field of 100
kHz is applied at a temperature of 100°C, the resulting hysteresis curve has an effective
magnetic permeability µa of at least 5,000 at magnetization B = 200 mT and an effective
magnetic permeability µa of at least 4,500 at magnetization B = 300 mT.
(8) The ferrite of any one of (1) to (7) which has a residual magnetic flux density
Br of up to 140 mT as measured in a DC magnetic field at a temperature of 25°C or
a ΔB value of at least 380 mT wherein ΔB = Bm - Br wherein Bm and Br are maximum magnetic
flux density and a residual magnetic flux density, respectively, as measured in a
DC magnetic field at a temperature of 25°C.
(9) A ferrite core for use in an electric power supply, characterized by comprising
the ferrite of any one of (1) to (8).
FUNCTION AND BENEFITS OF THE INVENTION
[0008] Since the manganese-zinc system ferrite of the present invention contains predetermined
amounts of silicon oxide, calcium oxide, tin oxide and/or titanium oxide, niobium
oxide, and zirconium oxide, it is minimized in power loss and increased in ΔB in a
relatively high frequency region (for example, of 10 to 500 kHz). The ferrite is then
useful to form cores in transformers required to produce an output of several watts
to several tens of watts as in business machines. Since the ferrite has an improved
µa-B curve and a high µa value, transformers for power supplies can be reduced in
size. These advantages are available over a wide temperature range while a fully low
power loss is maintained. at a practical service temperature of about 80 to 110°C.
[0009] Although some of the above-cited patent publications disclose subordinate compounds
as used in the present invention, none of them disclose specific combinations falling
within the scope of the invention.
[0010] For example, JP-A 198416/1993 discloses a Mn-Zn system ferrite which is based on
a base component consisting of Fe
2O
3, MnO and ZnO and contains as subordinate components SiC, CaO and at least one member
selected from the group consisting of niobium oxide, titanium oxide, antimony oxide,
tantalum oxide, vanadium oxide, zirconium oxide, tin oxide, aluminum oxide, cobalt
oxide, copper oxide, hafnium oxide, and silicon oxide. This patent publication, however,
lacks the description that addition of silicon oxide, calcium oxide, tin oxide and/or
titanium oxide, niobium oxide, and zirconium oxide is essential, and none of Examples
disclosed therein show the combined addition of these oxides. In Examples disclosed
therein, low losses are available when certain subordinate components are added although
no reference is made to Bm, Br, and ΔB at high frequency and DC as well as to effective
magnetic permeability (µa).
[0011] JP-A 267040/1993 discloses a Mn-Zn system ferrite which is based on a base component
consisting of Fe
2O
3, MnO and ZnO and contains as subordinate components Si
3N
4, CaO and at least one member selected from the group consisting of niobium oxide,
titanium oxide, antimony oxide, tantalum oxide, zirconium oxide, tin oxide, cobalt
oxide, and silicon oxide. This patent publication, however, lacks the description
that addition of silicon oxide, calcium oxide, tin oxide and/or titanium oxide, niobium
oxide, and zirconium oxide is essential, and none of Examples disclosed therein show
the combined addition of these oxides. In Examples disclosed therein, low losses are
available when certain subordinate components are added although no reference is made
to Bm, Br, and ΔB at high frequency and DC as well as to effective magnetic permeability
(µa).
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a crystalline structure photograph substituting for drawing, showing a
cross section of a ferrite core under an optical microscope.
[0013] FIG. 2 is a crystalline structure photograph substituting for drawing, showing a
cross section of a ferrite core under an optical microscope.
ILLUSTRATIVE EMBODIMENTS
[0014] Now, the illustrative embodiments of the present invention are described in detail.
The manganese-zinc system ferrite of the present invention contains manganese oxide,
zinc oxide, and iron oxide as main components, and silicon oxide, calcium oxide, tin
oxide and/or titanium oxide, niobium oxide, and zirconium oxide as subordinate components.
[0015] With respect to the content of the respective oxides in the main components, manganese
oxide is 30 to 41 mol%, preferably 33 to 41 mol% calculated as MnO, zinc oxide is
6 to 16 mol%, preferably 6 to 12 mol% calculated as ZnO, and the balance consists
of iron oxide. Outside this range, there result increased power losses, a minimum
temperature of lower than 60°C, a Curie point of lower than 200°C, lowering of Bm
and initial magnetic permeability (µi) in the high frequency region, or increased
Br.
[0016] The weight proportion of the subordinate components based on the main components
is as follows.
[0017] Silicon oxide is 50 to 250 ppm, preferably 70 to 200 ppm calculated as SiO
2. Calcium oxide is 200 to 1,500 ppm, preferably 300 to 1,000 ppm calculated as CaO.
By adding silicon oxide and calcium oxide in these ranges, there are achieved a reduction
of Br, an increase of ΔB (= Bm - Br), a reduction of power loss, an increase of Q
value, and an improvement in µa-B curve.
[0018] Tin oxide is up to 4,000 ppm calculated as SnO
2, and titanium oxide is up to 3,000 ppm calculated as TiO
2. The total of tin oxide and titanium oxide is at least 300 ppm, preferably at least
500 ppm. Preferred are those containing 500 to 4,000 ppm of tin oxide wherein the
tin oxide is contained alone or wherein up to 90% by weight of the tin oxide is replaced
by titanium oxide. By adding at least one of tin oxide and titanium oxide in these
ranges, there are achieved a reduction of Br, an increase of ΔB, a reduction of power
loss, and an improvement in µa-B curve, allowing for size reduction of cores.
[0019] Niobium oxide is from 100 to 500 ppm calculated as Nb
2O
5, and is preferably up to 400 ppm. Zirconium oxide is from 50 to 400 ppm calculated
as ZrO
2. By adding niobium oxide and zirconium oxide in these ranges, there are achieved
a critical reduction of power loss, a reduction of Br, an increase of ΔB, and an improvement
in µa-B curve.
[0020] In addition to these subordinate components, the ferrite of the present invention
may contain trace additive elements and impurity elements originating from raw materials.
Such elements include P, B, Al, Co, Cu, Li, Na, K, In, Bi, etc. To suppress their
influence on power loss and magnetic properties, the weight proportion of these elements
based on the main components should preferably be up to 200 ppm (0 to 200 ppm). In
particular, since P and B have a great influence on power loss and magnetic properties,
the weight proportion of P based on the main components should preferably be 0 to
30 ppm, more preferably 0 to 20 ppm, most preferably 0 to 10 ppm, and the weight proportion
of B based on the main components should preferably be 0 to 50 ppm, more preferably
0 to 30 ppm. This leads to improvements in Br, ΔB, µa and loss.
[0021] The ferrite of the invention preferably has an average crystal grain size of 10 to
30 µm, more preferably 10 to 20 µm. A smaller average grain size would lead to an
increased hysteresis loss whereas a larger average grain size would lead to an increased
eddy current loss.
[0022] The ferrite of the invention can have a power loss of up to 300 kW/m
3, especially up to 260 kW/m
3 at a temperature of 100°C when a sinusoidal AC magnetic field (maximum 200 mT) of
100 kHz is applied. Among the power losses, the eddy current loss can be reduced to
200 kW/m
3 or less, especially 170 kW/m
3 or less. While the hysteresis loss is proportional to a frequency and the eddy current
loss is proportional to the square of a frequency, the ferrite of the invention has
the advantage that no substantial increase of power loss occurs even in a high frequency
region in excess of 100 kHz because the eddy current loss at 100 kHz is relatively
small.
[0023] Also the ferrite of the invention follows a hysteresis curve when a sinusoidal AC
magnetic field of 100 kHz is applied at a temperature of 100°C. The hysteresis curve
has Bm of at least 350 mT, Br of up to 170 mT, especially up to 150 mT, and ΔB = Bm
- Br of at least 220 mT, often at least 250 mT, especially at least 280 mT. Its coercivity
Hc is generally up to 20 A/m, often up to 14 A/m, especially up to 13 A/m.
[0024] Further the ferrite of the invention has Br of up to 140 mT or ΔB of at least 380
mT as measured in a DC magnetic field at 25°C. It also has Bm of at least 520 mT and
Hc of up to 12.5 A/m, especially up to 12.0 A/m.
[0025] A smaller value of Br or a larger value of ΔB leads to a wider unsaturation region
which enables use at greater power and which is advantageous for minor loop driving
when mounted as a core.
[0026] Also the ferrite of the invention follows a hysteresis curve when a sinusoidal AC
magnetic field of 100 kHz is applied at a temperature of 100°C. The hysteresis curve
has an effective magnetic permeability µa of at least 5,000, especially at least 5,200
and generally up to about 7,000 at magnetization B = 200 mT. The effective magnetic
permeability µa at magnetization B = 300 mT is at least 4,500, often at least 4,800,
especially at least 5,500 and generally up to about 7,000. These allow cores to be
significantly reduced in size as compared with conventional cores.
[0027] From the ferrite of the invention there may be formed cores for use in electric power
supply transformers which will operate at a frequency of 10 to 500 kHz and a temperature
of about 80 to 110°C while their power is generally about 1 to 100 W.
[0028] The ferrite and power supply-forming ferrite core according to the invention are
manufactured by the methods mentioned below.
[0029] Raw materials used for the main components are powder oxides or powder compounds
which convert into oxides by heating. For example, iron oxide powder, manganese oxide
powder, manganese carbonate powder, zinc oxide powder, etc. may be used. They are
mixed and calcined and the calcined mixture is finely divided to a mean particle size
of about 1 to 3 µm. Calcining may be effected in air at a predetermined temperature
in the range of 800 to 1,000°C.
[0030] Raw materials used for the subordinate components are powder oxides or powder compounds
which convert into oxides by heating. In some cases, powders of metal elements which
are members of the subordinate components may be used.
[0031] The mixing ratio of the main components to the subordinate components should correspond
to the final composition. Raw materials of the main components and raw materials of
the subordinate components may be mixed before or after calcination.
[0032] Raw materials of the main components are not limited to the above-mentioned ones
and a powder of a composite oxide containing two or more metals may be used as a main
component raw material. Such composite oxide powder is generally prepared by oxidizing
and roasting chlorides. For example, a powder of a composite oxide containing Fe,
Mn and Zn can be prepared by oxidizing and roasting an aqueous solution containing
iron chloride, manganese chloride and zinc chloride. This composite oxide generally
contains a spinel phase. It is noted that since zinc chloride has a high vapor pressure,
a compositional shift often occurs. An alternative method is then to form a main component
raw material by preparing a powder of a composite oxide containing Fe and Mn from
an aqueous solution of iron chloride and manganese chloride and mixing the powder
with a zinc oxide powder or zinc ferrite powder. When the composite oxide powder resulting
from the oxidation roasting process is used as a main component raw material, it is
unnecessary to carry out calcination.
[0033] Thereafter, a mixture of main component raw materials and subordinate component raw
materials is combined with a small amount of a suitable binder such as polyvinyl alcohol
and atomized into particles having a particle size of about 80 to 200 µm by means
of a spray dryer or the like. The particles are then compacted and the compact is
fired in an atmosphere having a controlled oxygen concentration and at a temperature
in the range of 1,250 to 1,400°C, obtaining a ferrite.
EXAMPLE
[0034] Examples of the present invention are given below by way of illustration.
[0035] Ferrite core samples having the composition shown in Table 1 were prepared. First,
calcined raw materials of the main components and raw materials of the subordinate
components were mixed. The raw materials used for the main components were Fe
2O
3, Mn
3O
4 and ZnO, which were mixed and calcined at 900°C for 3 hours. The raw materials used
for the subordinate components were SiO
2, CaCO
3, SnO
2, TiO
2, Nb
2O
5 and ZrO
2. The raw materials of the subordinate components were added to the calcined raw materials
of the main components and they were mixed while pulverizing. The calcined material
was pulverized until a mean particle size of about 2 µm was reached. The resulting
mixture was combined with a binder and atomized into particles having a mean particle
size of 150 µm by a spray dryer. The particles were compacted and fired in an atmosphere
having a controlled oxygen partial pressure at 1,300°C for 5 hours, obtaining a toroidal
sample having an outer diameter of 31 mm, an inner diameter of 19 mm, and a height
of 8 mm. The samples were measured for proportion of constituent elements by fluorescent
X-ray analysis. The proportion of constituent elements was the same as the raw material
composition. It is noted that the content of P in Table 1 was measured by absorptiometry.
The samples was measured for boron content by ICP, finding a B content of up to 30
ppm in all the samples. It is noted that P and B originated from the starting oxides
such as iron oxide.
[0036] With a sinusoidal AC magnetic field of 100 kHz and 200 mT (maximum) applied, each
sample was measured for hysteresis loss (Phv), eddy current loss (Pev), and core loss
(Pcv) at 100°C. The results are shown in Table 2. It is to be noted that there is
a general relationship:
wherein Prv is a residual loss. The respective terms are:
Phv = αxf
Pev = βxf2
Prv = γ
wherein f is a driving frequency, and α, β and γ are constants. This gives the following.
Dividing the equation by f gives the following.
If γ is sufficiently small, formula III can be approximated to a linear expression
of f. Since the ferrites used in the respective samples had a sufficiently small value
of γ in a frequency zone of 25 to 500 kHz, Pcv = Phv + Pev is assumed in Table 2.
[0038] The samples had a mean grain size of 10 to 15 µm. FIG. 1 is a photograph under an
optical microscope of a cross section of sample No. 1. FIG. 2 is a photograph under
an optical microscope of a cross section of sample No. 12. FIGS. 1 and 2 show that
both the samples have an approximate crystal grain shape and approximately equal mean
grain size.
[0039] As shown in Table 2, the inventive samples are low in both hysteresis loss and eddy
current loss and hence, low in core loss. In general, the hysteresis loss decreases
as the grain size increases; and the eddy current loss decreases as the grain size
decreases. A comparison between FIGS. 1 and 2 reveals that the loss reduction in the
inventive samples does not depend on grain size.
[0040] Further, the inventive samples have high Hc and high ΔB so that they may be used
at high power. They also have good µa-B properties, and as a result, power supply
transformers can be reduced in size and power supplies using the same can be increased
in efficiency. More particularly, the core size can be made very small. The improved
efficiency allows for a lower input power and a reduced number of windings. While
the operating power is limited by the heat release which in turn, varies depending
on input power and core configuration, the core according to the invention allows
the input power to be increased because of reduced power losses.
[0041] It was found in connection with sample No. 12 that the core loss (especially eddy
current loss) increased when the weight proportion of silicon oxide was less than
50 ppm based on the main components, and that the core loss also increased when the
weight proportion of silicon oxide was more than 250 ppm. The core loss (especially
eddy current loss) increased, Br increased and ΔB decreased when the weight proportion
of calcium oxide was less than 200 ppm based on the main components, and the core
loss also increased when the weight proportion of calcium oxide was more than 1,500
ppm. Moreover, the temperature at which the core loss was minimized was below 60°C
when the weight proportion of tin oxide was more than 4,000 ppm based on the main
components and when more than 3,000 ppm of titanium oxide was added without adding
tin oxide.
[0042] It was also found in connection with sample No. 12 that when a mixture of tin oxide
and titanium oxide was used instead of tin oxide alone, there were obtained equivalent
properties to sample No. 12.
1. A ferrite
characterized by comprising
manganese oxide, zinc oxide, and iron oxide as main components and silicon oxide,
calcium oxide, tin oxide and/or titanium oxide, niobium oxide and zirconium oxide
as subordinate components, wherein
in the main components, the content of manganese oxide is 30 to 41 mol% calculated
as MnO and the content of zinc oxide is 6 to 16 mol% calculated as ZnO, and
the weight proportion of the subordinate components based on the main components is
such that
silicon oxide is 50 to 250 ppm calculated as SiO2,
calcium oxide is 200 to 1,500 ppm calculated as CaO,
tin oxide is up to 4,000 ppm calculated as SnO2,
titanium oxide is up to 3,000 ppm calculated as TiO2, and the total of tin oxide and titanium oxide is at least 300 ppm,
niobium oxide is from 100 to 400 ppm calculated as Nb2O5, and
zirconium oxide is from 50 to 400 ppm calculated as ZrO2, said ferrite being free from Si3N4.
2. The ferrite of claim 1 wherein the weight proportion of P based on the main components
is 0 to 30 ppm.
3. The ferrite of claim 1 or 2 wherein the weight proportion of B based on the main components
is 0 to 50 ppm.
4. The ferrite of any one of claims 1 to 3 which has a power loss of up to 300 kW/m3 at a temperature of 100°C when an AC magnetic field of 100 kHz and 200 mT is applied.
5. The ferrite of claim 4 which has an eddy current loss of up to 200 kW/m3 at a temperature of 100°C when an AC magnetic field of 100 kHz and 200 mT is applied.
6. The ferrite of any one of claims 1 to 5 wherein when an AC magnetic field of 100 kHz
is applied at a temperature of 100°C, the resulting hysteresis curve has a ΔB value
of at least 220 mT wherein △B = Bm - Br wherein Bm and Br are maximum magnetic flux
density and residual magnetic flux density, respectively.
7. The ferrite of any one of claims 1 to 6 wherein when an AC magnetic field of 100 kHz
is applied at a temperature of 100°C, the resulting hysteresis curve has an effective
magnetic permeability µa of at least 5,000 at magnetization B = 200 mT and an effective
magnetic permeability µa of at least 4,500 at magnetization B = 300 mT.
8. The ferrite of any one of claims 1 to 7 which has a residual magnetic flux density
Br of up to 140 mT as measured in a DC magnetic field at a temperature of 25°C or
a ΔB value of at least 380 mT wherein ΔB = Bm - Br wherein Bm and Br are maximum magnetic
flux density and a residual magnetic flux density, respectively, as measured in a
DC magnetic field at a temperature of 25°C.
9. A ferrite core for use in an electric power supply, characterized by comprising the ferrite of any one of claims 1 to 8.
1. Ferrit
gekennzeichnet durch den Gehalt an
Manganoxid, Zinkoxid und Eisenoxid als Hauptkomponenten und Siliciumoxid, Calciumoxid,
Zinnoxid und/oder Titanoxid, Nioboxid und Zirkonoxid als Nebenkomponenten, worin
bei den Hauptkomponenten der Gehalt an Manganoxid, berechnet als MnO, 30 bis 41 Mol-%
und der Gehalt an Zinkoxid, berechnet als ZnO, 6 bis 16 Mol-% beträgt, und der Gewichtsanteil
der auf die Hauptkomponenten bezogenen Nebenkomponenten so ist, daß
Siliciumoxid, berechnet als SiO2, 50 bis 250 ppm,
Calciumoxid, berechnet als CaO, 200 bis 1.500 ppm,
Zinnoxid, berechnet als SnO2, bis zu 4.000 ppm,
Titanoxid, berechnet als TiO2, bis zu 3.000 ppm, und die Gesamtmenge von Zinnoxid und Titanoxid mindestens 300
ppm,
Nioboxid, berechnet als Nb2O5, von 100 bis 400 ppm, und
Zirkonoxid, berechnet als ZrO2, von 50 bis 400 ppm sind, wobei der Ferrit frei von Si3N4 ist.
2. Ferrit nach Anspruch 1, worin der auf die Hauptkomponenten basierende Gewichtsanteil
an P 0 bis 30 ppm ist.
3. Ferrit nach Anspruch 1 oder 2, worin der auf die Hauptkomponenten basierende Gewichtsanteil
an B 0 bis 50 ppm ist.
4. Ferrit nach einem der Ansprüche 1 bis 3, welcher bei einer Temperatur von 100 °C einen
Leistungsverlust von bis zu 300 kW/m3 hat, wenn ein Wechselstrom-Magnetfeld von 100 kHz und 200 mT angelegt ist.
5. Ferrit nach Anspruch 4, welcher bei einer Temperatur von 100 °C einen Wirbelstromverlust
von bis zu 200 kW/m3 hat, wenn ein Wechselstrom-Magnetfeld von 100 kHz und 200 mT angelegt ist.
6. Ferrit nach einem der Ansprüche 1 bis 5, worin die resultierende Hysterese-Kurve einen
ΔB-Wert von mindestens 220 mT aufweist, wenn ein Wechselstrom-Magnetfeld von 100 kHz
bei einer Temperatur von 100 °C angelegt ist, wobei ΔB = Bm - Br ist, worin Bm und
Br jeweils die maximale magnetische Flußdichte und restmagnetische Flußdichte sind.
7. Ferrit nach einem der Ansprüche 1 bis 6, worin die resultierende Hysterese-Kurve eine
wirksame magnetische Permeabilität µa von mindestens 5.000 bei einer Magnetisierung
B = 200 mT und eine wirksame magnetische Permeabilität µa von mindestens 4.500 bei
einer Magnetisierung B = 300 mT aufweist, wenn ein Wechselstrom-Magnetfeld von 100
kHz bei einer Temperatur von 100 °C angelegt ist.
8. Ferrit nach einem der Ansprüche 1 bis 7, welcher eine in einem Gleichstrom-Magnetfeld
bei einer Temperatur von 25 °C bestimmte restmagnetische Flußdichte Br von bis zu
140 mT oder einen ΔB-Wert von wenigstens 380 mT hat, worin ΔB = Bm - Br ist, worin
Bm und Br jeweils die in einem Gleichstrom-Magnetfeld bei einer Temperatur von 25
°C bestimmte maximale magnetische Flußdichte und die restmagnetische Flußdichte sind.
9. Ferritkern zur Verwendung in einer elektrischen Stromversorgungsvorrichtung, gekennzeichnet durch den Gehalt des Ferrits nach einem der Ansprüche 1 bis 8.
1. Ferrite
caractérisée en ce qu'elle comprend :
en tant que composants principaux, de l'oxyde de manganèse, de l'oxyde de zinc et
de l'oxyde de fer, et en tant que composants secondaires de l'oxyde de silicium, de
l'oxyde de calcium, de l'oxyde d'étain et/ou de l'oxyde de titane, de l'oxyde de niobium
et de l'oxyde de zirconium, où
dans les composants principaux, la teneur en oxyde de manganèse calculée sous forme
de MnO est de 30 à 41 % molaires, la teneur en oxyde de zinc calculée sous forme de
ZnO est de 6 à 16 % molaires, et la proportion pondérale des composants secondaires
par rapport aux composants principaux est telle que
l'oxyde de silicium sous forme de SiO2 est de 50 à 250 ppm,
l'oxyde de calcium sous forme de CaO est de 200 à 1 500 ppm,
l'oxyde d'étain sous forme de SnO2 est au plus de 4 000 ppm,
l'oxyde de titane sous forme de TiO2 est au plus de 3 000 ppm, le total de l'oxyde d'étain et de l'oxyde de titane étant
au moins de 300 ppm,
l'oxyde de niobium sous forme de Nb2O5 est de 100 à 400 ppm, et
l'oxyde de zirconium sous forme de ZrO2 est de 50 à 400 ppm, ladite ferrite étant dépourvue de Si3N4.
2. Ferrite suivant la revendication 1, dans laquelle la proportion pondérale de P par
rapport aux composants principaux est de 0 à 30 ppm.
3. Ferrite suivant la revendication 1 ou 2, dans laquelle la proportion pondérale de
B par rapport aux composants principaux est de 0 à 50 ppm.
4. Ferrite suivant l'une quelconque des revendications 1 à 3 ayant une perte de puissance
allant jusqu'à 300 kW/m3 à une température de 100°C quand un champ magnétique de courant alternatif de 100
kHz et 200 mT est appliqué.
5. Ferrite suivant la revendication 4, ayant une perte en courant parasite (ou courant
de Foucault) allant jusqu'à 200 kW/m3 à une température de 100°C quand un champ magnétique de courant alternatif de 100
kHz et 200 mT est appliqué.
6. Ferrite suivant l'une quelconque des revendications 1 à 5, dans laquelle, quand un
champ magnétique de courant alternatif de 100 kHz est appliqué à une température de
100°C, la courbe d'hystérésis résultante à une valeur △B d'au moins 220 mT où ΔB =
Bm - Br, Bm et Br étant la densité de flux magnétique maximal et, respectivement,
la densité de flux magnétique résiduel.
7. Ferrite suivant l'une quelconque des revendications 1 à 6, dans laquelle quand un
champ magnétique de courant alternatif de 100 kHz est appliqué à une température de
100°C, la courbe d'hystérésis résultante a une perméabilité magnétique efficace µa
d'au moins 5 000 pour une magnétisation B = 200 mT et une perméabilité magnétique
efficace µa d'au moins 4 500 pour une magnétisation B = 300 mT.
8. Ferrite suivant l'une quelconque des revendications 1 à 7, ayant une densité de flux
magnétique résiduel Br allant jusqu'à 140 mT mesurée dans un champ magnétique de courant
continu à une température de 25°C ou une valeur ΔB d'au moins 380 mT où ΔB = Bm -
Br, Bm et Br étant la densité de flux magnétique maximal et, respectivement, la densité
de flux magnétique résiduel mesurée dans un champ magnétique de courant continu à
une température de 25°C.
9. Noyau de ferrite pour utilisation dans une alimentation en puissance électrique, caractérisé en ce qu'il comprend une ferrite suivant l'une quelconque des revendications 1 à 8.